What are the symptoms of Neuroleptic Malignant Syndrome?

Neuroleptic Malignant Syndrome (NMS) is a potentially life-threatening condition often associated with the use of antipsychotic medications. The hallmark symptoms of NMS include fever, tachycardia (increased heart rate), and extreme rigidity. These symptoms are critical indicators of the syndrome and often present together. The high fever is particularly concerning and can indicate severe autonomic disruption, while extreme rigidity reflects a significant alteration in muscle tone. The presence of tachycardia indicates the body's response to the stress caused by the syndrome.

In contrast, the other symptoms associated with different psychiatric conditions are not characteristic of NMS. Involuntary facial movements pertain to tardive dyskinesia, excessive inner restlessness relates to akathisia, and delusions and hallucinations are more aligned with psychosis or other primary psychiatric disorders, rather than NMS. Therefore, these symptoms do not capture the essence of what NMS entails, making the correct answer focused on the physiological signs commonly observed in this serious medical emergency.